Thermoplastics are useful in manufacturing articles in the sectors of the automotive industry and transport, the industry of electrical and electronic appliances, including household electricals, the packaging industry, such as that of microwavable food packaging, in the construction and decoration industry, in the mechanical industry and, in general, in the industry of plastics, which relates to many and varied applications such as in toys or office goods.
One of the most widely used classes of thermoplastics for these applications is that of rigid styrenic thermoplastics and, more particularly, that of rigid and transparent styrenic thermoplastics, such as polystyrene, which exhibits a number of advantages in this type of application (optical and mechanical properties, low cost, ease of use, etc.), but which, unfortunately, does not exhibit very high heat or solvent resistance.
The skilled person has therefore sought to copolymerize the styrene with other monomers, capable of providing the eventual copolymer with an improvement in its heat and solvent resistance, in relation to homopolystyrene, while retaining good processability properties (capacity to be readily transformable). Accordingly U.S. Pat. No. 2,971,939 describes a polymerization process producing copolymers of styrene and maleic anhydride or blends of a styrene homopolymer with a copolymer of styrene and maleic anhydride, which have an improved heat distortion temperature while retaining the processability of the material.